In the related art, as shown in FIGS. 19 and 20, submerged membrane separation device is installed in a treatment tank and submerged in water 12 to be treated, e.g., sewage. A submerged membrane separation device 13 includes multiple membrane elements 14 and multiple membrane joining/fixing members 15. The membrane elements 14 are arranged at predetermined spacing in the thickness direction. The membrane joining/fixing members 15 are disposed on both ends of the membrane elements 14. The ends of the membrane elements 14 are joined and connected by the membrane joining/fixing members 15.
The membrane elements 14 are flat plates or sheets, each having filtration membranes 16 on the front and back sides. The membrane joining/fixing member 15 has a water collecting pipe 17 for collecting water permeated through the filtration membranes 16. On the upper end of the water collecting pipe 17, a suction pipe 18 is formed. Further, an air diffuser 19 is provided below the membrane elements 14.
Pressures in the membrane elements 14 are reduced from the suction pipes 18 by, e.g., a suction pump to enable the filtration membranes 16 to capture solid contents such as sludge in the water 12 to be treated. Subsequently, water having permeated through the filtration membranes 16 and flown into the membrane elements 14 is collected as treated water in the water collecting pipe 17, and then the treated water is drained out of the water collecting pipe 17 through the suction pipe 18.
At this point, air sent from the air diffuser 19 produces an air-lift effect to generate upward flows 20 in a gas-liquid phase between the membrane elements 14. The upward flows 20 clean the membrane surfaces of the membrane elements 14.
The submerged membrane separation device 13 further includes spacing members 21 that keep spacing between the filtration membranes 16 between the adjacent membrane elements 14. As shown in FIGS. 20 and 21, the spacing members 21 are comb-like members having teeth 22 and are respectively attached to the upper and lower ends of the membrane elements 14. The teeth 22 of the upper spacing member 21 are inserted between the upper ends of the membrane elements 14 and the teeth 22 of the lower spacing member 21 are inserted between the lower ends of the membrane elements 14.
With this configuration, the upper spacing member 21 keeps spacing 23a between the upper ends of the membrane elements 14 at predetermined spacing and the lower spacing member 21 keeps spacing 23b between the lower ends of the membrane elements 14 at the predetermined spacing.
The submerged membrane separation device 13 including the spacing members 21 is described in, e.g., Patent Literature 1.
Citation List
Patent Literature
    Patent Literature 1: Japanese Patent Laid-Open No. 2000-237551